Targeted genome modification is a powerful tool for genetic manipulation of eukaryotic cells, embryos, and animals. For example, exogenous sequences can be integrated at targeted genomic locations and/or specific endogenous chromosomal sequences can be deleted, inactivated, or modified. Current methods rely on the use of engineered nuclease enzymes, such as, for example, zinc finger nucleases (ZFNs) or transcription activator-like effector nucleases (TALENs). These chimeric nucleases contain programmable, sequence-specific DNA-binding modules linked to a nonspecific DNA cleavage domain. Each new genomic target, however, requires the design of a new ZFN or TALEN comprising a novel sequence-specific DNA-binding module. Thus, these custom designed nucleases tend to be costly and time-consuming to prepare. Moreover, the specificities of ZFNs and TALENS are such that they can mediate off-target cleavages.
Thus, there is a need for a targeted genome modification technology that does not require the design of a new nuclease for each new targeted genomic location. Additionally, there is a need for a technology with increased specificity with few or no off-target effects.